The invention relates to a sensor array.
German patent application 101 58 053.3 describes a sensor array with at least two sub-bridges, which are coupled together to form at least one Wheatstone bridge and wherein each of the sub-bridges is equipped with at least two magnetoresistive sensor elements. These sensor elements are sensitive to the magnetic field strength of an applied magnetic field along a measurement direction, and are designed to deliver a measurement signal as a function of a field component of the magnetic field, designated a measurement field, measured in the measurement direction. Herein, at least two of the sensor elements in each of the sub-bridges exhibited barber pole structures with differing alignments. The location coordinates of the sensor elements of at least one of the sub-bridges and the location coordinates of the sensor elements of at least one of the other sub-bridges along a coordinate axis running in the measurement direction are selected to differ from each other to a predetermined degree.
The described sensor array already has a high interference immunity against magnetic interference fields, and enables a reliable operating mode even under onerous operating conditions.
It is an object of the invention to create a sensor array with a further improved interference immunity against magnetic interference fields.
This object is achieved in accordance with the invention by means of a sensor array with at least two sub-bridges, which are coupled together to form at least one Wheatstone bridge and which are equipped, in each of the sub-bridges, with at least two magnetoresistive sensor elements, wherein the sensor elements are sensitive to the magnetic field strength of an applied magnetic field along a measurement direction, and the sub-bridges are designed to deliver a measurement signal as a function of a field component of the magnetic field, designated a measurement field, measured in the measurement direction, wherein, further, in a first of the sub-bridges at least two of the sensor elements exhibit barber pole structures with differing alignments, in a second of the sub-bridges at least two of the sensor elements are designed without barber pole structures, and the measurement signals of the first sub-bridge at least largely coincide with the measurement signals of the second sub-bridge in a specified range of values around a zero point of the magnetic field strength of the measurement field.
The sensor array in accordance with the invention does not just exhibit a further improved interference immunity against magnetic interference fields, but also supplies measurement signals with significantly greater signal amplitudes than the sensor array described in German patent application 101 58 053.3. It also transpires that production tolerances in the manufacture of the sensor array in accordance with the invention influence the dependence of the measurement signal on the measurement field to a much lesser extent than in the case of the sensor array described in German patent application 101 58 053.3.
In accordance with an advantageous development of the invention, location coordinates of the sensor elements of the first sub-bridge and location coordinates of the sensor elements of the second sub-bridge along a coordinate axis running in the measurement direction are selected so that they differ from one another to a predetermined extent. As a result, especially high signal amplitudes can be achieved for the measurement signals.
In a different embodiment of the invention, the measurement field is non-homogeneous at least in the measurement direction. A magnetic field of this kind is also designated as divergent in the measurement direction; its magnetic field lines, which are aligned essentially perpendicular to the measurement direction in the area of the spatial span of the sensor array, also exhibit at least one further directional component in the measurement direction, which additionally varies along the measurement direction. When a magnetic field of this kind is applied to the sub-bridge(s), especially those designed to have sensor elements without a barber pole structure, the operating point of this sub-bridge or the operating points of these sub-bridges are shifted in relation to the working point of the sub-bridge or the working points of the sub-bridges which comprise sensor elements with barber pole structures. This gives rise to a change in the sensitivity of the sub-bridge(s) with sensor elements without barber pole structures as compared with an external homogeneous magnetic field. In particular, the working points of the different sub-bridges are selected in this manner in such a way that the different sub-bridges exhibit matching sensitivities as compared with the said external homogeneous magnetic field.
An especially simple, robust development of the sensor array in accordance with the invention is achieved when the applied magnetic field is generated by an auxiliary magnet designed as a permanent magnet.